Tire/wheel assembly

ABSTRACT

A tire/wheel assembly includes a wheel having a rim, a pneumatic tire fitted to the rim of the wheel and a run-flat support member, the pneumatic tire having a tread surface and a hollow space, the tread surface having circumferential grooves extending in a circumferential direction of the tire, the run-flat support member being disposed in the hollow space of the pneumatic tire and having an annular shell and elastic rings, the annular shell comprising a support surface formed radially outward having a convexly curved surface portion with an annular apical line or face and two leg portions formed radially inward, the elastic rings supporting the two leg portions on the rim. The apical line or apical face of the convexly curved surface portion is offset in a direction of a center axis of rotation of the wheel so as not to be located in a position corresponding to the circumferential grooves when viewed from a radial direction of the wheel.

TECHNICAL FIELD

The present invention relates to a tire/wheel assembly, and, moreparticularly, to a tire/wheel assembly which can improve durabilitythereof.

TECHNICAL BACKGROUND

In response to demands in the market, there have been proposed manytechnologies which allow a vehicle to urgently travel several hundredkilometers even when a pneumatic tire is punctured while running. Amongthese many proposals, those disclosed in Japanese Patent Laid-OpenPublication No. 10-297226 and Published Japanese Translation of a PCTApplication No. 2001-519279 have enabled run-flat traveling bysupporting a punctured tire by a support member which is fitted onto arim in a hollow space of the pneumatic tire assembled to the rim.

The above run-flat support member comprises an annular shell having ansupport surface formed radially outward in the form of a convexly curvedsurface and two leg portions located radialy inward, and elastic ringsattached to the two leg portions, and is supported on the rim via theelastic rings. The run-flat support member allows existing wheels andrims to be used without any specific modification, and, therefore, canbe advantageously adopted without causing confusions in the market.

There are also known tire/wheel assemblies that allow run-flat travelingby supporting the inner surface of a punctured tire by the radiallyouter support surface of an annular run-flat insert member, formed froma rigid material such as metal or resin in such a shape as a “T” or “I”shape, which is fitted onto a rim in a hollow space of the pneumatictire assembled to the rim.

However, when a run-fat traveling distance up to the destruction of atire is examined on tire/wheel assemblies to which the above-mentionedrun-flat support member or run-flat insert member is attached usingpneumatic tires with different tread patterns, the run-flat travelingdistance varies significantly according to the tread patterns. Inparticular, when pneumatic tires having circumferential groovesextending in a tread surface in a circumferential direction of the tireare used for tire/wheel assemblies, the run-flat traveling distancetends to be shorter, and there is a problem that durability thereof islowered.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a tire/wheel assemblyin which when a pneumatic tire having a circumferential groove extendingin a tread surface in a circumferential direction of the tire is used,durability can be improved.

In order to achieve the above object, a tire/wheel assembly according tothe present invention comprises a wheel having a rim, a pneumatic tirefitted to the rim of the wheel and a run-flat support member, thepneumatic tire having a tread surface and a hollow space, the treadsurface having a circumferential groove extending in a circumferentialdirection of the tire, the run-flat support member being disposed in thehollow space of the pneumatic tire and having an annular shell andelastic rings, the annular shell comprising a support surface formedradially outward having a convexly curved surface portion with anannular apical line or face and two leg portions formed radially inward,the elastic rings supporting the two leg portions on the rim, whereinthe apical line or apical face of the convexly curved surface portion isoffset in a direction of a center axis of rotation of the wheel so asnot to be located in a position corresponding to the circumferentialgroove when viewed from a radial direction of the wheel.

Another tire/wheel assembly according to the present invention comprisesa wheel having a rim, a pneumatic tire fitted to the rim of the wheeland a run-flat insert member, the pneumatic tire having a tread surfaceand a hollow space, the tread surface having a circumferential grooveextending in a circumferential direction of the tire, the run-flatinsert member being disposed in the hollow space of the pneumatic tireand having an annular support surface with two edges disposed radiallyoutward for supporting an inner surface of the pneumatic tire duringrun-flat traveling, wherein the two edges of the annular support surfaceare offset in a direction of a center axis of rotation of the wheel soas not to be located in a position corresponding to the circumferentialgroove when viewed from a radial direction of the wheel.

According to the present invention mentioned above, during run-flattraveling, the run-flat support member supports the inner surface of thepneumatic tire with the apical line or apical face of the convexlycurved surface portion of the support surface thereof being not engagedwith a thin portion of the tread portion in which a circumferentialgroove exists, but being engaged with a thick portion thereof, or therun-flat insert member supports the inner surface of the pneumatic tirewith the two edges of the support surface thereof being not engaged witha thin portion of the tread portion in which a circumferential grooveexists, but being engaged with a thick portion thereof, thereby allowingdurability to be improved because of suppressing the occurrence of thedestruction at the circumferential groove.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a main part of an embodiment ofa tire/wheel assembly according to the present invention.

FIG. 2 is an enlarged cross-sectional view showing a main part ofanother run-flat support member used for a tire/wheel assembly accordingto the present invention.

FIG. 3 is a cross-sectional view showing a main part of an alternativeembodiment of a tire/wheel assembly according to the present invention.

FIG. 4 is a cross-sectional view showing a main part of anotheralternative embodiment of a tire/wheel assembly according to the presentinvention.

FIG. 5 is an explanatory view showing an another example of acircumferential groove of a pneumatic tire used for a tire/wheelassembly according to the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

The embodiments of the present invention will be described in detailbelow with reference to the drawings.

FIG. 1 is a cross-sectional view illustrating a main part of anembodiment of a tire/wheel assembly according to the present invention,in which reference numeral 1 denotes a rim in the outer periphery of awheel, reference numeral 2 denotes a pneumatic tire, and referencenumeral 3 denotes a run-flat support member.

The pneumatic tire 2 includes a tread surface 2A having a plurality ofcircumferential grooves 2B extending straight along a circumferentialdirection of the tire, which define ribs 2R therebetween. The rim 1,pneumonic tire 2, and run-flat support member 3 are formed in an annularshape coaxially about a center axis of rotation of the wheel (notshown), and the run-flat support member 3 is placed in a hollow space 2Yof the pneumatic tire 2 mounted on the rim 1.

The run-flat support member 3 comprises an annular shell 4 formed froman annulus of a rigid material such as metal or resin in order tosupport the weight of a vehicle via a punctured tire, and right and leftelastic rings 5 formed of an elastic material such as rubber or elasticresin in order to stably support the annular shell 4 with respect to therim 1.

The metal used for the annular shell 4 may include, for example, steel,aluminum and the like. The resin may be either of thermoplastic resin orthermosetting resin. The thermoplastic resin may include nylon,polyester and the like, and the thermosetting resin may be epoxy resin,unsaturated polyester resin, etc. The resin may be used alone or may beemployed as fiber-reinforced resin blended with reinforcing fibers.

The elastic rings 5 may be formed of any kind of rubber or resin as longas the annular shell 4 can be stably supported. The rubber may include,for example, natural rubber, isoprene rubber, styrene-butadiene rubber,butadiene rubber, butyl rubber, etc. The elastic resin may be foamedresin such as foamed polyurethane.

The annular shell 4 is formed so that it has an outer diameter smallerthan the inner diameter of an inner surface 2 a of the pneumatic tire 2in order to maintain a constant distance therebetween, and includes anannular support surface 6 having two convexly curved surface portions 6a, each being radially outwardly convex in shape when viewed in thecross section orthogonal to the tire circumferential direction. Theconvexly curved surface portions 6 a have a predetermined curvatureradius and are arranged along a width direction of the shell. Thesupport surface 6 is spaced apart from the inner surface 2 a of thepneumatic tire 2 when the pneumatic tire 2 is under a normal condition,and when the pneumatic tire 2 is punctured, the support surface 6supports the inner surface 2 a of the flattened tire.

The annular shell 4 has two side walls radially inward which are formedas leg portions 7, and each elastic ring 5 is attached to the radiallyinner side of each leg portion. The elastic rings 5 are fittinglyengaged with right and left rim seats ls to support the annular shell 4,thereby not only mitigating vibrations of and impacts upon the annularshell 4 from a punctured tire, but also preventing slipping relative tothe rim seats ls. The elastic rings stably support the annular shell 4.The elastic rings 5 are formed so that the inner diameter thereof is inthe approximately same size as the inner diameter of the beads of thepneumatic tire 2.

The above-mentioned convexly curved surface portions 6 a each have anapical line x which connects apexes thereof, the apical line x beinglocated between the circumferential grooves 2B and being offset towardsa direction of the wheel rotation center axis (the left or rightdirection in the drawing) so that the apical line x is not identical tothe circumferential groove 2B when viewed from the radial direction ofthe wheel.

The run-flat support member 3, when assembled to a rim, is inserted intothe interior of the pneumatic tire 2, and the elastic rings 5 are fittedto the rim seats ls of the rim 1 together with the beads 2 of thepneumatic tire 2 simultaneously.

In tire/wheel assemblies which employed a pneumatic tire having a treadsurface with circumferential grooves extending along a circumferentialdirection of the tire, the inventors made an observation of pneumatictires which busted up during run-flat traveling, resulting in that thedestruction of each tire occurred along the circumferential grooves,which made the run-flat traveling impossible.

When the relation between the circumferential grooves and each run-flatsupport member was studied, it was realized that, in the case where,when viewed in the radial direction of the wheel, the apical line of theconvexly curved surface portion which supported the tire was identicalto a circumferential groove where the thickness of the tread was thethinnest, tire destruction occurred earlier and the run-flat travelingdistance was shorter because the run-flat support member supported thetire at the thinnest portion of the tread.

The present invention is based on the discovery of this fact, and theapical lines x of the convexly curved surface portions 6 a are offset ina direction of the wheel rotation center axis so that the apical lines xof the convexly curved surface portions 6 a are not identical to thecircumferential grooves 2B when viewed from the radial direction of thewheel. This allows the apical lines x of the convexly curved surfaceportions 6 a to engage with the portions (thick portions) of ribs 2R ofthe tread 2D and the run-flat support member 3 to support the innersurface 2 a of the pneumatic tire 2 at the thick portions of the tread2D during run-flat traveling, thereby suppressing the destruction at thecircumferential grooves 2B. Therefore, durability can be improved.

It is preferable in view of more effective improvement of durabilitythat the apical line x of each convexly curved surface portion 6 a bepositioned so as to be spaced away one forth or more of a wheel rotationaxis direction length L (rib width) between the opening ends 2B1 ofcircumferential grooves 2B from each opening end 2B1 thereof. It is morepreferable that the apical line x of each convexly curved surfaceportion 6 a be located substantially in the center between the openingends 2B1 (the center of the rib 2R).

The position of the apical line x is determined in the state of the tirebeing filled with air before punctured, since the tire reduces itsdiameter almost without changing the position of the circumferentialgrooves 2B in the direction of the wheel rotation center axis when thetire is in the run-flat traveling state after punctured and deflated.The position of the apical line x, however, may be determined, based onthe tire in the run-flat traveling condition.

The support surface 6 of the run-flat support member 3 may be one havingconvexly curved surface portions 6 a with an annular apical face y whichis flat in cross section, as shown in FIG. 2, instead of the convexlycurved surface portions 6 a with the apical line x as described above.In this case, the apical face y is arranged not to overlap relative tothe circumferential groove 2B as mentioned above. Preferably, the apicalface y may be spaced away from the circumferential groove 2B asdescribed above.

Exemplified is the run-flat support member 3 having the annular shell 4with the support surface 6 which comprises two convexly curved surfaceportions 6 a. The number of the convexly curved surface portions is,however, not limited to two, but may be one or three or more. In thiscase also, the apical line x or apical face y of each convexly curvedsurface potion 6 a is arranged to be offset relative to thecircumferential groove 2B, thereby allowing durability to be improved.

Two or more convexly curved surface portions are preferably arranged. Byforming the support surface 6 in this way so as to arrange two or moreconvexly curved surface portions 6 a, the contact points of the supportsurface with the tire inner surface 2 a are dispersed in two or more,and localized wear on the tire inner surface 2 a is reduced, therebymaking it possible to extend a distance that a vehicle can endurerun-flat traveling.

FIG. 3 shows an alternative embodiment of a tire/wheel assemblyaccording to the present invention, in which a run-flat insert member 13is employed in the alternative of the above-mentioned run-flat supportmember 3.

The run-flat insert member 13 comprises an annulus which is I-shaped incross section, having a cylindrical base portion 14, a ring portion 15annularly protruding on the radially outer surface 14 a of the baseportion 14, and a support portion 16 annularly disposed on the outercircumference of the ring portion 15; the base portion 14, ring portion15 and support portion 16 are formed as a unitary structure from a rigidmaterial such as metal or resin.

The metal used for the run-flat insert member 13 may include, forexample, steel, aluminum and the like. The resin may be either ofthermoplastic resin or thermosetting resin. The thermoplastic resin mayinclude nylon, polyester and the like, and the thermosetting resin maybe epoxy resin, unsaturated polyester resin, etc. The resin may be usedalone, or may be employed as fiber-reinforced resin blended withreinforcing fibers.

The radially outer surface of the support portion 16 is formed as asupport surface 16 a for supporting the inner surface 2 a of thepneumatic tire 2 during run-flat traveling. The annular support surface16 a has the substantially same shape as the inner surface 2 a of thepneumatic tire 2 which is supported during ran-flat traveling.

The support surface 16 a has two edges e which are offset toward adirection of the wheel rotation center axis so that each edge e is notidentical to the circumferential groove 2B when viewed from the radialdirection of the wheel. The run-flat insert member 13 is secured to therim 1 through an insert member supporting element 17.

The tire/wheel assembly using the run-flat insert member 13 as mentionedabove can also improve durability, because the both edges e of thesupport surface 16 a are in engagement with the portions (thickportions) of ribs 2R of the tread 2D during run-flat traveling and thedestruction at the circumferential grooves 2B are suppressed.

FIG. 4 shows another alternative embodiment of a tire/wheel assemblyaccording to the present invention, which has the same structure as theabove-mentioned tire/wheel assembly in FIG. 3 except that the run-flatinsert member has two support portions 16 for supporting the innersurface 2 a of the pneumatic tire 2 during ran-flat traveling, eachsupport portion 16 being disposed via a ring portion 15 on each side ofthe radially outer surface of the base portion 14. The run-flat insertmember also has left and right elastic rings 20, which are formed of anelastic material such as rubber or elastic resin, protruding from theinner circumference of the base portion 14, the elastic rings 20 beingfittingly attached to the rim 1 as insert member supporting elements.Each edge e of the support surfaces 16 a is offset as described above,also when the run-flat insert member 13 having a plurality of suchsupport portions 16 is employed, thus allowing the same effect to beobtained.

The foregoing run-flat insert member 13 is not limited to those whichare fixedly attached to the rim 1 through the insert member supportingelement 17 or the elastic rings 20, but is one which is directly fixedlyattached to the rim 1 therewithout, or one which is mounted on a slidebase attached to the rim 1; the run-flat insert member 13 may be any ofrun-flat insert members which include an annular support surface 16 awith edges e on both sides thereof disposed radially outward forsupporting the inner surface 2 a of the pneumatic tire 2.

It is preferable in view of more effective improvement of durabilitythat each edge e of the support surface 16 a of the run-flat insertmember 13 between the circumferential grooves 2B be positioned so as tobe spaced away one forth or more of the wheel rotation axis directionlength L between the opening ends 2B1 of circumferential grooves 2B fromeach opening end 2B1 thereof, as described above. It is more preferablethat each edge e be located substantially in the center between theopening ends 2B1.

Each edge e of the support surfaces 16 a positioned tire-outwardly ofboth outermost circumferential grooves 2B as shown in FIG. 4 may belocated so as to be spaced apart one forth or more of a wheel rotationaxis direction length M between the tire-outer opening end 2B1 of theoutermost circumferential groove 2B and the contact end Q of the treadsurface 2A from the opening end 2B1 towards the tire outer side.Preferably, each edge e may be positioned substantially in the centerbetween the tire-outer opening end 2B1 of the outermost circumferentialgroove 2B and the contact end Q of the tread surface 2A.

Note that the contact end Q referred herein is the contact end of thetread surface 2A in which the tire/wheel assembly has an air pressure of200 kPa and load of 80% of the maximum load ability described in JATMA(JATMA YEAR BOOK 2001) is applied thereto.

The position of each edge e is determined, as described above, in thestate of the tire being filled with air before punctured, since the tirereduces its diameter almost without changing the position of thecircumferential grooves 2B relative to the direction of the wheelrotation center axis when the tire is in the run-flat traveling stateafter punctured and deflated. The position of each edge e, however, maybe determined, based on the tire in the run-flat traveling condition.

In the embodiments illustrated above, the circumferential grooves 2B,which are straight in shape, are exemplified, but as shown in FIG. 5,the circumferential grooves 2B may be zigzag grooves. In such a casealso, the apical line x or apical face y of the support surface 6 a andeach edge e of the support surface 16 a may be positioned so as to bespaced away from each opening end 2B1 one forth or more of the wheelrotation axis direction length L, M as discussed above. When thecircumferential grooves 2B are zigzag in shape like this, the positionof each opening end 2B1 is defined to be the center position A of thezigzag width of the opening end 2B1 extending in a zigzag path.

In the above-mentioned embodiments, exemplified are the pneumatic tires2 which include a tread surface 2A having ribs 2R defined by thecircumferential grooves 2B, but the pneumatic tire 2 may be one that hasa block pattern with blocks defined by circumferential grooves andlateral grooves; in this case also, the same effect can be obtained byusing the foregoing run-flat support members 3 or run-flat insertmembers 13.

EXAMPLE 1

Prepared were tire/wheel assemblies of the present invention (example A)and the comparison (comparative example A), having the same tire size of205/55R16 and the same rim size of 16×6 1/2JJ, the tire/wheel assemblyof the present invention having a construction in which a run-flatsupport member is arranged such that the apical line of each convexlycurved surface portion thereof is positioned approximately in the centerbetween the circumferential grooves, as shown in FIG. 1, and thecomparative tire/wheel assembly having the same construction as thetire/wheel assemblies of the present invention except that the apicalline of each convexly curved surface portion is located in a positioncorresponding to the circumferential groove.

An evaluation test for durability was conducted on each of the testtire/wheel assemblies in accordance with the following measurementmethod. The results shown in Table 1 were obtained.

Durability

Each of the test tire/wheel assemblies having an air pressure of 0 kPawas fitted as a front right wheel of a front-wheel-drive vehicle with adisplacement of 2.5 liters and the vehicle was driven at 90 Km/h in atest course. A distance until the vehicle could no longer run wasmeasured. The results of the measurement were evaluated by an indexnumber, with the index number of the comparative tire/wheel assemblybeing 100. The greater the index number is, the better the durability.

The same sized tires and rims as described above were used for wheels ofthe vehicle other than the front right wheel, with the tires having anair pressure of 200 kPa. TABLE 1 Comparative Example A Example ADurability 185 100

As can be seen from Table 1, the tire/wheel assembly of the presentinvention is capable of improving durability.

EXAMPLE 2

Prepared were tire/wheel assemblies of the present invention (example B)and the comparison (comparative example B), having the same tire sizeand the same rim size as in Example 1, the tire/wheel assembly of thepresent invention having a construction in which a run-flat insertmember is arranged such that each edge of the support surface thereof ispositioned approximately in the center between the circumferentialgrooves, as shown in FIG. 3, and the comparative tire/wheel assemblyhaving the same construction as the tire/wheel assembly of the presentinvention except that each edge of the support surface is located in aposition corresponding to the circumferential groove.

An evaluation test for durability was conducted on each of the testtire/wheel assemblies in accordance with the measurement method shown inExample 1. The results shown in Table 2 were obtained. TABLE 2Comparative Example B Example B Durability 175 100

As can be seen from Table 2, the tire/wheel assembly of the presentinvention is capable of improving durability.

As illustrated above, according to the present invention, the run-flatsupport member is arranged such that the apical line or apical face ofeach convexly curved surface portion of the support surface thereof isoffset in a direction of the wheel rotation center axis so as not to belocated in a position corresponding to the circumferential groove whenviewed from the radial direction of the wheel, or the run-flat insertmember is arranged such that each edge of the support surface thereof isoffset in a direction of the wheel rotation center axis so as not to belocated in a position corresponding to the circumferential groove whenviewed from the radial direction of the wheel, thereby allowingdurability of the tire/wheel assembly using a pneumatic tire having atread surface with circumferential grooves extending in thecircumferential direction of the tire to be improved.

INDUSTRIAL APPLICABILITY

The tire/wheel assembly of the present invention having theaforementioned excellent effect can be used very effectively as atire/wheel assembly which is mounted to a vehicle and allows run-flattraveling.

1. A tire/wheel assembly comprising: a wheel having a rim; a pneumatictire fitted to the rim of the wheel, the pneumatic tire having a treadsurface and a hollow space, the tread surface having a circumferentialgroove extending in a circumferential direction of the tire; and arun-flat support member disposed in the hollow space of the pneumatictire, the run-flat support member having an annular shell and elasticrings, the annular shell comprising a support surface formed radiallyoutward having a convexly curved surface portion with an annular apicalline or face and two leg portions formed radially inward, the elasticrings supporting the two leg portions on the rim, wherein the apicalline or apical face of the convexly curved surface portion is offset ina direction of a center axis of rotation of the wheel so as not to belocated in a position corresponding to the circumferential groove whenviewed from a radial direction of the wheel.
 2. A tire/wheel assemblyaccording to claim 1, wherein the tread surface of the pneumatic tirehas a plurality of circumferential grooves, the apical line or apicalface of the convexly curved surface portion being located between thecircumferential groves so as to be spaced away one forth or more of awheel rotation axis direction length L between opening ends of thecircumferential grooves from each opening end thereof in the directionof the wheel rotation center axis.
 3. A tire/wheel assembly according toclaim 2, wherein the apical line or apical face of the convexly curvedsurface portion is positioned approximately in the center between thecircumferential grooves.
 4. A tire/wheel assembly comprising: a wheelhaving a rim; a pneumatic tire fitted to the rim of the wheel, thepneumatic tire having a tread surface and a hollow space, the treadsurface having a circumferential groove extending in a circumferentialdirection of the tire; and a run-flat insert member disposed in thehollow space of the pneumatic tire, the run-flat insert member having anannular support surface with two edges provided radially outward forsupporting an inner surface of the pneumatic tire during run-flattraveling, wherein the two edges of the annular support surface areoffset in a direction of a center axis of rotation of the wheel so asnot to be located in a position corresponding to the circumferentialgroove when viewed from a radial direction of the wheel.
 5. A tire/wheelassembly according to claim 4, wherein the tread surface of thepneumatic tire has a plurality of circumferential grooves, each of thetwo edges of the support surface being located between thecircumferential groves so as to be spaced away one forth or more of awheel rotation axis direction length L between opening ends of thecircumferential grooves from each opening end thereof in the directionof the wheel rotation center axis.
 6. A tire/wheel assembly according toclaim 5, wherein each of the two edges of the support surface ispositioned approximately in the center between the circumferentialgrooves.